The present invention relates to ejector systems for ejecting ordnance stores, e.g. bombs, missiles or other material containers, from an aircraft and more particularly to store ejector systems which are capable of imparting an angular rate of movement or angular attitude to the store as it is ejected.
When a store is released from an aircraft in flight it is necessary to forcibly eject the store away from the flow field developed around the aircraft to prevent a collision with the aircraft, due to upward currents, etc. When the store is forcibly ejected from the aircraft, the store is subjected to various forces which have a profound effect on its flight pattern. One factor which effects the force field during release and the flight pattern of the store after release is the attitude and acceleration of the plane. Another factor which must be considered in order to assure proper projection of the store at the target is the various center of gravity locations in various stores which influence the pitch and pitch rate of the store. Due to various locations of the center of gravities, generally a single ejector is undesirable since the force of the ejector at a position other than the center of gravity will develop a moment. Dual ejectors alleviate this problem, but when utilizing ejectors at the fore and aft positions, it is necessary to synchronize the movement, regardless of force differentials, so as to assure proper pitch or attitude for the store.
It has been found that by utilizing two substantially independent hydraulic circuits having equal fluid volumes and synchronized pistons with substantially equal piston areas, each of the two ejectors will move a proportional amount regardless of whether the force against one ejector is greater than the other. This is generally known in the art as dual dependency. With a dual dependency capability the effect of an offset center of gravity is minimized. At the same time it may be desirable to make the degree of extension of each of the ejectors independently adjustable so that a predetermined pitch may be imparted to the store. An example of a dual dependent system of ejecting stores with independent adjustments of the degree of ejector extension for pitch control is found in U.S. Pat. No. 3,974,990 to Holt et al. The system disclosed in Holt et al consists of two hydraulic ejector assemblies which are synchronized and operated from a pressurized gas power system output piston. Pitch attitude and pitch rate control are achieved through the use of floating pistons within accumulating cylinders which have adjustable stops to vary the volume of fluid detracted from the corresponding ejectors. It is also known in the art that the use of a stepped piston assembly achieves synchronous, independent, hydraulic fluid flow as disclosed in Ser. No. 797,897, now abandoned, filed by Holt et al on May 17, 1977.
Another store ejector device with pitch control is disclosed in U.S. Pat. No. 4,043,525 to Jakubowski wherein an adjustable metering rod is used to apportion fluid between two thruster pistons. In an alternate embodiment, Jakubowski discloses the use of a rotary apportioning device comprising an apertured, rotating cylinder. However, neither of the Jakubowski embodiments is dual dependent since by interconnecting the flow to the two ejectors, a force differential at one of the ejectors will result in increased flow to the opposite ejector and, therefore, an uncertain attitude for the release store.
It can be appreciated by those skilled in the art that both aforementioned patents disclose store release systems with limited variation possible with respect to pitch and pitch rate. In Jakubowski, the flow to each of the two ejector pistons is generally proportional, and in Holt et al the effect of the accumulator cylinders results generally in an incremental delay. In the above described devices, the pitch and pitch rates are generally interdependent as the selection of flow distributions is generally limited. Therefore, there is a general need in the store ejector art for an ejector system with the capability of ejecting stores at a multitude of pitches and pitch rates to accommodate the diverse physical characteristics of various stores so as to insure a safe and predictable flight pattern for the store. Furthermore, there is a general need for a store ejector unit having dual dependency such that an increased resistance incurred by one ejector will not result in more fluid travelling to the opposite ejector, to thereby insure a predictable/repeatable stroke with control of acceleration, stroke time, and end of stroke velocity.